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Madurai Kamraj University (2008)

Eco physiological study of multipurpose tree species in semi arid eco climatic region of Madurai

Gnaana Saraswathi

Titre : Eco physiological study of multipurpose tree species in semi arid eco climatic region of Madurai

Auteur : Gnaana Saraswathi

Université de soutenance : Madurai Kamraj University

Grade : Doctor of Philosophy (PhD) 2008

Sommaire partiel
The significant differences between the four species in all leaf gas exchange parameters, both in diurnal and seasonal trends, were apparent especially during the dry summer season. As in many Mediterranean and tropical species, the stomatal closure in D. sissoo during summer constitutes a mechanism to cope with diurnal and seasonal water deficits. H. binata remained with open stomata during the summer season, influencing the CO2 assimilation.

The net carbon gain and biomass was comparatively higher in D. sissoo and A. lebbeck than in H. binata and C. siamea. Even though D. sissoo and H. binata are deciduous, H. binata has obvious advantages in avoiding unfavourable periods, for instance, the midday depression of photosynthesis as it is likely to be one of the most important factor to understand acclimation of photosynthesis to irradiance in natural environment. But in D. sissoo the major adaptation to seasonal severe drought appears to be leaf senescence which was observed during the dry summer time (March).

The seasonal course of carbon gain and water turnover exhibited in D. sissoo and A. lebbeck shows that stomatal acclimation to the weather patterns may change either by increasing carbon gain on the one hand or limiting water loss on the other. As long as there is no water stress, stomata may acclimate to allow higher PN, together with a higher water loss especially during and after the rainy season when the soil water content is large. On the other hand, during periods of persistent high atmospheric evaporative demand due to high temperature, VPD, and depleted soil water buffering, acclimation limits excessive water loss as a first priority, thereby allowing lower carbon gain.

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Page publiée le 11 février 2021